Bravia TV Question

Discussion in 'General Electronics Chat' started by Fish2222, Feb 19, 2015.

  1. Fish2222

    Thread Starter New Member

    Feb 19, 2015
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    Hi guys. I am new here, but not necessarily new to fixing TV's. I have a Sony KDL-52V5100 TV that has an issue that I can't figure out. It attempts to power up, but turns back off in about 10 seconds. It does kick the back light on, and the power relay turns on, and then back off when it shuts down. I have tried pulling the LVDS cable while the backlight is on, but it doesn't seem to effect the LCD at all. I wasn't sure which firmware the board had on it, but I downloaded the newest version, put it on aflash drive, and plugged it on and turned it on. It acted like it did the update, and when it was done, the pic/timer light turned yellow, while the standby light was red, and then the pic/timer light turned green. The power supply seems to have all of the correct voltages shown by the writing by the plugs. Does anyone have any idea? I would think since I don't have a standby light until after a flash attempt, that is the key, but I am not sure. I also disconnected all board except the power supply and the mainboard, and it still does the same thing.
     
  2. Robartes

    Member

    Oct 1, 2014
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    Often when a TV does something like this, it is the capacitors in the power supply that have gone south. I don't know the Sony Bravia, but it probably has a switched mode power supply with some largish (couple of 100 to 1000 uF) capacitors on the secondary side. Inspect those for obvious damage (bulging, evidence of leaking), measure their ESR if possible, and replace any faulty ones.
     
  3. sheldons

    Active Member

    Oct 26, 2011
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    NONONONO.....do not go reloading any software ....unless you know for sure you have a software error with the ssb.....that fault is probably due to a faulty invertor transformer on the invertor pcb-some models do have two boards fitted- one master one slave invertor. Before you start check the smps for faults, a service manual is needed before you make any checks.do you not have Compaire? Sometimes with this particular make the software gives an error code which flashes the standby led a number of times depending on the fault.....
     
  4. Fish2222

    Thread Starter New Member

    Feb 19, 2015
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    Thanks guys. I am thinking it is the main board, since it does the same thing when I disconnect everything except the mainboard and power supply. I have checked the power supply for all the correct voltages and it is correct. There are no bulging caps either.
     
  5. bwilliams60

    Active Member

    Nov 18, 2012
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    What is Compaire?
     
  6. Fish2222

    Thread Starter New Member

    Feb 19, 2015
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    All of the caps seems to test out fine. I am not getting any flashing lights. Just a green power light from the time it comes on till the time it turns off.
     
  7. wayneh

    Expert

    Sep 9, 2010
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    How so? Do you have an ESR meter? Capacitance is the last thing to go, ESR goes first.
     
  8. Fish2222

    Thread Starter New Member

    Feb 19, 2015
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    I just have a capacitance meter. They all seem to test within 10%, even though they are all still soldered to the board.
     
  9. wayneh

    Expert

    Sep 9, 2010
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    Sadly, that's not good enough. There is a kit I've seen for a very nice multimeter that includes an ESR meter, and you could build your own kit if you have some parts and a breadboard. (I've done it.) But all of these options sound like more work than just replacing them, since I'm pretty sure they have to be removed from the board to be tested anyway.
     
  10. ian field

    Distinguished Member

    Oct 27, 2012
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    Before I got an ESR meter, I weeded out quite a lot of duds just using my senses.

    For one thing; an electrolytic with high ESR in a high speed energy conversion circuit will get hot - but care is needed on live circuits, the aluminium can isn't isolated.

    Running hot for any length of time will degrade the plastic sleeve round the capacitor, this will sometimes give the game away. Everyone knows about the bulged tops when the electrolytics get hot and build up a head of steam, they can also vent where the leads pass through the seal - the loss of electrolyte becomes a partial vacuum when they cool, this is sometimes visible by sunken tops.

    Sometimes the electrolyte corrodes its way out around one of the leads, usually leaving a gelatinous stain between the cap & PCB - sometimes going over the soldering will give the game away, heating one particular joint will produce a sizzling noise and a nasty smell - fair bet there's a dud electrolytic on the other side.

    With experience you get a feel for what capacitors weigh - one missing most of its electrolyte will feel lighter than it should.
     
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  11. wayneh

    Expert

    Sep 9, 2010
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    I used to scoff when everyone advised "replace the caps" to almost every repair project. I had replaced exploded electrolytics, but the notion that a capacitor could be bad that looked fine and even has rated capacity, seemed far-fetched. Then I repaired a power supply this summer by nothing but replacing all the caps. I later confirmed that several had high ESR. Now I'm a believer and another voice for "replace the caps".
     
  12. wayneh

    Expert

    Sep 9, 2010
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    Just curious, can you do useful ESR measurements without removing them?
     
  13. ian field

    Distinguished Member

    Oct 27, 2012
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    A) in most SMPSU circuits, the capacitor gets hot because of the internal losses that dissipate as heat.

    B) both the analogue and digital ESR meters I've bought since, do in circuit testing.

    My first attempt at an ESR meter was a bridge rigged to ignore Xc and only see the series resistance. I used a 400kHz ceramic resonator for the oscillator and put that through a divide 2 flip-flop for equal mark space ratio, so I ended up with a 200kHz test frequency - unfortunately that produced enough ripple current that ended up across the internal series resistance for it to heat up. As the temperature increased, the ESR decreased - sometimes it would sink down as low as an acceptable reading.

    It was also apparent that freshly unsoldered capacitors, still hot from the iron - could read about normal, leave them on the bench for a while to cool and you can read their true ESR.
     
  14. Robartes

    Member

    Oct 1, 2014
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    That must impress the natives no end if you manage to pull it off successfully!
     
  15. wayneh

    Expert

    Sep 9, 2010
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    Works with batteries, too!
     
  16. atferrari

    AAC Fanatic!

    Jan 6, 2004
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    What you would need to do anyway to replace them.
     
  17. sheldons

    Active Member

    Oct 26, 2011
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    Ok Compaire is a servicing software which you have to pay for but it caters for many models of lcd, plasma, crt sets etc.it allows you to run any set -even if you have a no display fault and allows the set to easily be started in service mode so you can make adjustments etc-service manual is still needed as that gives you all the relevant info you need.....also if the signal to switch the invertor on is missing from the ssb or the protection on the invertor is at fault that will stop the set working
     
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  18. ian field

    Distinguished Member

    Oct 27, 2012
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    The worst that can happen is you replace one or two capacitors that aren't causing a problem. Although there's no immediate tangible gain - I'm sure those not urgently needed replacements make a slight dent in the number of subsequent call-backs.

    Generally speaking, if an electrolytic is running hot - if it isn't already failing, it will do soon.
     
  19. Fish2222

    Thread Starter New Member

    Feb 19, 2015
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    The only issue I have is that it doesn't stay on long enough to see about heat on a cap. There are a few caps in parallel that I do need to unsolder to test so I hope to have time soon to check it out. And I can't find anything about that Compaire software online.
     
  20. ian field

    Distinguished Member

    Oct 27, 2012
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    One thing you could try is warming it up with a hair dryer, ESR improves with rising temperature so it might start and keep going.

    Its a risky tactic though! - its a common thing with set top boxes that seem to be running just fine, but the capacitors are quietly developing high ESR. So the owner unplugs everything to go on holiday - when they get back and plug everything in, the STB either fails to start or goes bang. The electrolytics which had been working fine at their normal working temperature have been allowed to cool.

    Its something I've heard from PC users many times - the PSU gets reluctant to start and continues to deteriorate, they find if they keep flicking the on off switch, it will eventually catches. Each attempt puts a little more energy into the faulty cap heating it up a little till the ESR drops - its only a matter of time before it starts up with no regulation and takes the MOBO with it!

    Its probably worth replacing all the smallest electrolytics on the PSU primary side with good quality low ESR types, even if they're not the cause of this problem, they can make a mess when they fail later!

    Some UK component suppliers for consumer goods, stock replacement kits of electrolytics for a selection of popular equipments - considering the damage that can occur due to ESR problems, this is often the cheaper way of going about the repair.
     
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